Untold Memories
by Wordsock
Summary: Eleven years ago, experiment ended in calamity and W.D. Gaster was forced to choose between becoming a murderer or a parent. Today he and his son Sans share a life in the city. But after a visit to the lab, Sans can't shake the words of a stranger from his mind. There's something that he doesn't know, and as his father's nightly visits become more frequent, a chilling dread ensues.
1. Prologue

**_(important) Note from Wordsock:_**

 _"EY EY ATTENTION. ...Ahem. All right, thanks to everyone who's read and followed this, but big changed are going to happen. I'm restarting._

 _Q. BUT WHYYY_

 _A. The writing's crap. I've been caring more about the story than making it interesting to read. I can do better than this, and I've PROVEN that. I'm 1.5k words in on the new prologue and I can already see all the detail that's missing from this shit. Plus my headcanons have evolved somewhat and this story doesn't reflect my real thoughts. It's cheesy._

 _Q. WHEN WILL IT BE UPLOADED_

 _A. When I'm done writing the prologue I'll upload it as a new story and delete this one. It will take longer because I want to focus on QUALITY not QUANTITY. Thanks :D"_

 **Prologue**

Perhaps, if he wanted to, he could run.

He could turn his back and abandon everything, walk away from all those years of fascination and discovery and let it all crumble into the nothingness from which it had come. He could let it fall into the crimson abyss of the flashing lights and those sirens that screeched their ugly song of death.

If he wanted to, he could just leave the others to clean up his mess of fire and dust, or die trying to finish what he had started.

 _No._ Gaster shook that foul idea from his mind, his face twisting with a grimace of disgust. His actions had already cost enough lives this day. What kind of murderer would it turn him into to leave another person for dead? His friend and co-worker, Smoy. His best teacher and assistant, Rythe. _Him,_ the little one that rested in Gaster's thin, bony arms; they all deserved better than the chances that Gaster had given them.

Something buzzed inside his lab coat. Gaster adjusted his hold on _him_ and reached into the pocket to draw out the phone. Rythe. _Thank goodness._

"Doctor!" called the tinny voice from the other end of the line. There was no picture, but Gaster could hear the distress in her words. "Oh my God – was that an explosion?"

"Nine explosions, actually," Gaster corrected her, his voice trembling almost as much as his knees were. His ghostly white skin was cold and clammy, the cell kept slipping out of his palm, and for some reason he didn't see the flashing red light when he opened his right eye.

"Oh, jeez. Are you hurt? Hold on, I'm coming." The call ended after cutting to some loud static noise, and Gaster was left once more in the darkened and half-destroyed laboratory with the flashing warning lights and sirens, the weight of the thing of his arms dragging him down to his knees.

 _My son._

 _My doom._

Whenever he brought himself to look at the thing in his arms, those were the two phrases that entered his mind. They swam around and around, fighting each other in a bloody battle for a place in Gaster's perception of 'correct'.

He knew what this thing was; more than a failed experiment, it was the most dangerous thing that he had ever held. Its soul, that string of life within, didn't quite fit in the vessel that had been made for it – there was just too much energy for the body to contain, and at any moment the tissue could collapse and unleash that raw life force on everything nearby. _Just like the others did._

That's what it was; a grenade. But it was also _alive_. When it stretched open its eye sockets, curled those chubby finger bones around Gaster's spindly thumb, stared up at him with that big cheesy grin, it was easy to forget the danger. It was more than a test subject – it was a child.

 _My son._

 _My doom._

A shrill calling of his own name cut through Gaster's thoughts. "Doctor! Oh hell, the floor –"

"Yes, watch your feet." He had been so engrossed with his own thoughts that he forgot what a safety hazard the lab had become – the explosions had littered the ground with sharp-edged shards of thick glass, and the suspension liquid had since seeped through the cracks in the tiles, leaving a slippery, clear residue. It came as no surprise to him that Rythe had difficulty keeping her balance; the smooth, yellow skin on the soles of her bare feet weren't helpful in the way of giving her a grip on the floor. But still she came to Gaster and knelt by his side. He felt those immense brown eyes examining him as they always had done whenever he messed up – only this time, they were checking rather than judging him.

"Rythe –"

"What?" she chirped a little too quickly. Gaster swallowed and locked eyes with her as she removed the phone from his feeble hold.

"S-Smoy. Smoy. Is he all right?" he finally managed to cough up. His voice didn't seem to be working properly – it was a little too high-pitched and hoarse-sounding.

"He went home early, Doc."

He couldn't stop the weak smile that spread across his face. Smoy was safe. Rythe was unhurt. Gaster hadn't killed his assistants yet.

"Rythe," he began after a while, "It's fine. I'm fine. You can go come, I'll tell Asgore we're… I'll tell him what happened. Go home."

"But Doc, your eye."

"Nevermind that," Gaster sighed, "I'll be fine. You can go home."

"What about the subject?"

 _Oh._ The child. Gaster hadn't thought about him.

 _My son._

 _My doom._

Weighing the odds seemed a near-impossible task at this moment. How could he decide what to do with the little skeleton resting in the crook of his arm? He had no right to choose whether something should be allowed to live or not, but at the moment there were no shoulders for the decision to rest on but his. He couldn't burden Rythe with his own mistake.

 _But what do I do?_ Should he sever that cord of life and protect what little he had left? That would give Gaster both a sense of security and the label of 'killer'. No. He couldn't do that. The realisation rose in him, faster than a flash-flood; he had a duty to this child. If Gaster had cursed him with a soul that shouldn't have ever existed, wasn't it his responsibility to see that its life wasn't as miserable as its creation?

 _My son. My son. My son._ The words attacked his every thought, pecking at his mind whenever he contemplated his second option. With every passing second he became yet more aware of what his own soul knew it wanted. And between being a murderer and a father, Gaster knew what he preferred, too. _That settles it._

"I'll… Take him home," Gaster croaked, tearing his gaze away from the child and turning instead to face his assistant. "He's my son, so I might as well treat him like it."


	2. Chapter One

**Chapter One**

Sans glanced up at the figure looming in the doorway, then quickly dropped his head to the pillow and slowed his breathing, pretending to be asleep. _So it's one of those nights._

No matter how much trust he had in his father, it always did unnerve Sans to catch a glimpse of that dark shape silhouetted against the hallway's bleak yellow light. The slender, spindly arms that hung limp by his crooked torso made him look awfully akin to a spider. The thought of those strange little creatures made Sans' neck crawl, and it took a tremendous effort not to squirm on the spot. _Don't be rude towards spiders,_ Sans heard his father warn in that too-cheerful voice.

After he heard those tell-tale footsteps fading beyond earshot, Sans dared again to open his eyes. The luminous digits of his bedside clock stared back at him. _11:58._ He'd stayed up too late again. With a muted sigh he turned over, prying himself away from the numbers as they came and went in their never-ending countdown to the next hour. Sans didn't want to fall asleep; the next morning promised merry hell, and giving in to his exhaustion would only bring so-called dawn straight to him. But he never won the battle against weariness, and within minutes he had drifted back into a dream.

Morning looked no different to the dead of night. Still the same shadows grabbed at Sans from every nook and cranny as he rolled out of bed and clothed himself in a white tee and shorts. Still he felt the prickle of the chill, rolling air on his neck as he trudged through the hallway and into the lounge, where his eyes were assaulted by colours that didn't belong. Too warm and bright, the rich green carpet and vibrant paintings on the walls didn't seem fitting.

"Yo, Sans," called a familiar voice from behind a free-standing bookshelf. "No breakfast?"

"You had the last of the ketchup last night." Sans reminded his father in a tense grunt as he padded across the room to meet him. He was lying along the length of the leather sofa. His legs were folded over each other, feet resting on the arm and pink slippers moving up and down as he wiggled his toes. Wrapped up in an equally pink dressing gown and with a pair of thick, rectangular spectacles constantly sliding down his face, W.D. Gaster looked much less akin to a hungry spider during the day time. He wasn't scary at all, actually; Gaster had a strange aura about him that perhaps would have better suited a rocking chair-bound grandmother.

"Oh, yeah. Sorry – you'll have to go without." Gaster pushed his glasses back up his face. They slid down again.

"I'm not hungry," Sans said as he turned to the wall, disinterested in whatever small talk his father wanted to make. Unless Gaster was going to tell him that he could stay at home, where he was safe between the brightly-coloured walls, Sans didn't want to know.

"Well, that's a first. Must be all those nerves, right?" _Look at me when I'm talking to you,_ Sans heard his father say. He turned back to look at the man on the sofa.

"Yeah."

"I don't even get what you're so afraid of. Any other kid would be jumping up and down, you know."

"Yeah."

Gaster frowned at Sans and abruptly sat up as straight at his back would allow, thoroughly searching the boy from a distance with his one dark eye. One of his pink slippers fell off.

"Sans, c'mere," he said, placing a cold hand on the boy's arm. "It's _fine._ It's a lab, I work there every day, all that's going to happen is a couple of tests that you don't have to have anything to do with. All right?"

Sans hunched his shoulders over and looked away from his father, escaping the grip of that invasive stare. "…Yeah." he finally managed to get out, even if it sounded somewhat pathetic. Why he was even trying was beyond him; Sans was, to be truthful, a terrible liar. Even though his mouth was always stretched wide in a permanent grin, Gaster seemed to be able to see through him, deciphering every thought and emotion that ever flickered in his mind.

With a brisk pat to the shoulder and a comforting smile, Gaster sent Sans off to find something warmer to wear, telling him that 'it's cold out and we've got quite a ways to walk'. Sans wasn't really sure if skeletons could freeze to death, but feeling cold wasn't pleasant, so he meekly headed back to his room and did as he was told.

When the pair met up at the front door, Gaster cast his son the same smile as before and patted him on the head. Standing next to Gaster was like standing beside a pine tree. It made Sans feel rather small, like a squat duckling waddling aside a swan.

Gaster had changed clothes, too; instead of a dressing gown, he now wore a black shirt under his white lab coat, which was covered in blotches and stains from various coffee and chemical spills. His feet were still covered only by his slippers.

Sans had chosen a puffy charcoal-coloured overcoat and a pair of thick walking shoes. His father had warned him of the cold, but glancing again at the man in a shirt and lab coat, he got the sense that he had perhaps overdressed for the occasion.

"Ready?" Gaster queried cheerfully. 'No,' Sans wanted to say – hearing the word 'laboratory' sent a discomforting shudder down his back, and not in the way that the word 'mathematics' did. _I wish I could just go to school instead._

"Ready." Sans lied through gritted teeth. He saw Gaster's smile falter for a second, but he was quick to turn away and rub the back of Sans' skull. A comforting gesture.

"All right, then. Let's go." Gaster slid the chain away, turned the knob and pushed open the door.


	3. Chapter Two

**Chapter Two**

"We cross here. Hold my hand."

Sans reluctantly took Gaster's extended hand in his palm and loosely held it between his index finger and thumb as his father led him across the street. The road was wide and bare, the flat tarmac still flat and fluid even after decades of wear.

Sans couldn't remember the last time he saw a car in New Home. Maybe nobody in the city owned one. It's not like they were needed, after all; the city was compact, most of the buildings squashed close together in ugly stone blocks with the majority of residential lots and businesses taking up the easternmost part of the area. Everything else was either a farm or a factory. The little cargo trucks that ran to and from the west were the only motor vehicles that made good use of the roads.

"Dad?"

"Yeah, kid?" Gaster craned his neck to peer down at his son. His glasses were halfway down his face.

"Is… Is Doctor Rythe going to be at the Lab, too?"

Gaster paused for a moment, pushing the spectacles back up to his eyes. "No, she's going to be on leave for the rest of this week. I might give her more, actually – raising a kid alone is tricky business, she'll be up to her eyes in it."

"Oh." Sans pulled the neck of his coat up to his chin. Every movement that he made through the frigid air sent another icy claw tracing down Sans' spine, triggering a bout of shivers and a throbbing ache deep in his bones. He wondered how Gaster could possibly stride forwards as carefree as he was, with so little regard for the temperature despite being dressed so lightly.

"Meanwhile we've got a guy called Chemblin working there instead. Oh, you'll like him. He's real nice. Makes good coffee, too."

"Is he as smart as her?"

Gaster chortled softly and released the boy's hand to scratch at the fissure in his forehead. "I don't think anyone's as smart as Rythe. Actually, Sans, you're pretty clever. Maybe you can help me finish building my new blaster prototypes."

"Maybe." _Or maybe definitely not,_ he corrected himself, his eyes flitting back and forth. Doors were appearing from all sides now that they had entered the industrial half of the city, where monsters came and went in packs of twenty or thirty and the air was thick with magical residue. Somewhere amongst the bustle was an elevator that would take them into an apartment building that led to Hotland, where the Lab was. Gaster said that the CORE workers lived in that building.

"Is that the elevator?" Sans asked for about the tenth time as he gestured to yet another rather plain-looking double door built into the wall that they were approaching.

"That's the one!" he exclaimed cheerily. Sans didn't know whether to be relieved or anxious. "Give me a second, I'll just…" Gaster wandered towards the door and seemed to wrestle with some sort of panel on the side of the frame for a few minutes. Meanwhile Sans couldn't help but count the number of gold coins that he would have to add to the swear jar later on; not only was his father's crude choice of words mildly amusing, but he found that the numbers in his mind helped to ease his nerves. The twisting sensation in his abdomen ebbed a little bit more with every half-whispered 'shit', 'fuck' or 'goddamn it' that slipped through Gaster's jaws.

Eventually the two doors slid open, revealing a tiny cubicle panelled with silvery metal. _It's small,_ Sans thought, a grim look returning to his face. _It's really, really small._ He was beginning to think that he might prefer to stay out in the cold. In the cold, he wouldn't be trapped between steel walls, suspended above the ground where nobody could get in or out. _Nobody can get in or out._

Gaster backed away from the panel and stepped into the elevator, holding out an arm to beckon Sans inside. It seemed to take every ounce of willpower he could muster to step inside that steel cage with the doors that would snap shut and lock them both inside that small, small space like a pair of trapped birds.

 _It's an elevator,_ Sans reminded himself, feeling a tremor start in his knees again as the doors closed and the floor suddenly lurched downwards. _It's supposed to be small. It's supposed to be moving._ A bead of sweat trickled down his forehead and dripped from the top of his socket onto his cheek. Sans found himself standing pressed against his father's side, the stained cotton of the lab coat clenched tightly in his white fist. Gaster didn't say anything, but Sans could feel his father's touch against his back.

 _Ping!_

The movement of the elevator slowed and stopped, and the nausea that Sans had left on the ground level caught back up with him. He massaged some of the wooziness from his head with a couple of thick fingertips, then stumbled after his father, who was starting towards the doors as they pulled apart to reveal a dank-looking hallway.

"Don't mind the mess, Sans, we won't be here for long," Gaster cleared his throat, straightening his sleeves and lab coat as he started on his way through the hall. Sans nearly gagged on the heavy air that carried the sour stench of rot and must. He could see mildew and black mould creeping up the damp drywall between doors, and every few seconds he caught a glimpse of something crawling along the ceiling.

"In fact, give me your coat or else you'll boil as soon as we leave."

Clumsily, Sans fumbled with the zipper of his puffy overcoat and slipped it off into Gaster's waiting arms. It was warmer and muggier in the apartment building, so no icy claws snagged on his ribs. Gaster threw the coat over his left shoulder and flashed a toothless grin at his son from behind the glasses that kept slipping down. Sans smiled back weakly, for once thankful for the permanent grin that stretched across his face. It made him look more confident than he thought he could ever feel, even if Gaster could see straight through it. _We're almost at the lab. We're going to be there soon. It's just through some door along this corridor. We're almost at the lab._

"Is – is that where we're meant to go?" Sans finally choked out, raising a trembling arm to point at a door slightly bigger than the ones by its side. Its hinges were less rusty and the paint had a certain sheen to it that the others were lacking. A coded lock panel similar to the one on the elevator was bolted to the frame.

"Not this time. That's the one that goes to the CORE." _Oh._ Sans, of course, knew all about the CORE. Its inventor had told him about how it worked enough times, and he also warned Sans of its dangers. _It has to be secured with all sorts of puzzles,_ Gaster had said, _just so that no adventurers wander inside and fall in._ What 'falling in' meant was another unanswered question to Sans. He didn't even know if there was anything to fall into - but if there was, he didn't think his curiosity was reason enough to try and find out.

His thoughts were interrupted by a husky, upbeat-sounding voice. "'Ey, Doc!" it called. Sans suddenly found himself alone, as his father had hopped away to greet the voice's owner. It was a strange, skinny viper of a man with red skin. He had just a single eye that sat atop his large, flat head, which was taken up mostly by his wide, snapping mouth.

"Mornin', Chemblin," Gaster beamed, clapping the monster on the back in the same way that he did with Sans. "Did you forget something? I thought you'd be back at the lab with Smoy."

"Nah, sorry, Doc. I gotta go relay a message to one of the CORE guys. You know who I'm talkin' 'bout."

"Ah, right. Hey, before you go, say hi to my boy, would you? Sans! Come here, kid, this is Chemblin."

Sans swallowed hard and followed Gaster's instruction, approaching the stranger with the caution of a frightened alley cat. Upon closer inspection, the man's red skin was scaly and shimmered in a whole spectrum of colours when it caught the light shining from the fixtures on the cracked and peeling ceiling. Strange tooth-like growths sprouted from his jaws, which stretched back almost all the way to his neck. Sans suppressed a shudder and politely reached out a clammy hand for Chemblin to shake. Chemblin took it in his paw and shook vigorously, only releasing Sans when he spoke.

"Sans!" Chemblin hollered. Sans winced at the volume of the voice, but stammered a quick 'hi' in return. "Name's Chemblin. I work at the lab with the Doc, see? He told me he had a pretty cool son, what, a few hundred times?" The monster broke into a roar of laughter.

"Yes, maybe a slight exaggeration." Gaster mentioned as the noise subsided, rubbing the crack in his skull again and casting Chemblin a sidelong glance. "Well, he's off school, so I thought I'd take him to work with me. All of the teachers fell ill suddenly, you see –"

Chemblin shot Gaster a knowing glance and snorted, his lip curling up at the edges. "Oh, I wonder whose fault that is." Gaster stiffened and smiled nervously, adjusting his grip on Sans' overcoat. "Anyway – Sans, how old are ya?"

Sans jumped. He didn't expect the conversation to turn back to him so soon. Had he even been listening? What was the question?

"He's eleven. Twelve in a couple months, actually," Gaster chirped quickly. He had taken the bullet in Sans' place. _Thanks, Dad._

"'Ey, big boy. Anyhow, I have to go send off that message. Be back at the lab in a few, 'right? See ya, Doc. Kiddo." With that last word, Chemblin slithered away to fiddle with the panel at the door he had seen before, leaving Sans and Gaster standing in the silent aftermath of the lab assistant's loud and boisterous presence.

"Well," Gaster said finally, straightening up and facing Sans again. They both took a deep breath in unison, but then Sans remembered the uncleanliness of the air around him and coughed whatever spores he had just inhaled back out. "Shall we go? The door's just ahead." With a nod, the younger skeleton followed his father through the far door and a world of fire unfolded around them.


	4. Chapter Three

**Chapter Three**

Hotland. That was the name given to the place with the fire and the churning magma and the air that was warm enough to make the skin of Sans' bones prickle. It was a suiting name, the boy thought, but perhaps it didn't quite do it justice. His arms were already damp with hot sweat. _How can something so close to New Home be so different?_

"So, what did you think of Chemblin?" Gaster piped between ragged breaths. _Even he's having trouble handling the heat._ "Nice guy, huh?"

"He's okay. I don't like how loud he is, though."

"Oh, he's just enthusiastic. Doesn't look that young, but he's fresh out of college, you know."

Sans shrugged. He wasn't really interested in Chemblin. He wasn't interested in the lab, either, but he couldn't do anything to stop himself from zooming towards it on the conveyor belt that his father had led him to. _It lets us bypass the puzzles,_ he had explained. Sans watched as the building grew from a flickering speck in the heat haze to a tower of white concrete that stretched up and up and up...

The building was ugly, decorated only by flecks of red dust and a sign at the top with the word 'LABORATORY' slapped on in bright scarlet paint. Every time Sans saw it he felt that same pang of shock. Or something like shock, at least; he'd spent the entire morning dreading the moment when he would have to enter that building, so he had been expecting it for a long time.

 _What are you even afraid of?_ he heard his own voice asking. It was mocking him. _You're cowardly. You're paranoid._

"Is something wrong, Sans?" Gaster pried. _Nothing's wrong. You're just a coward._ "Still nervous?" Sheepishly the boy nodded. He found himself wringing his hands, so he shoved them into the pockets of his shorts and wiped the dampness off on the fabric inside. 'Nervous' didn't begin to describe the twisting, wrenching sensation that he felt right then. Not for the first time, he thought of home. He thought of how he could just bounce back to his bedroom if he wanted. That way he wouldn't have to go inside.

 _No,_ his voice sneered, _Look at his face. Look at how happy he is_ _._ Sans swallowed again. It was true, he could see it – beneath the concern for Sans, his father's one eye glimmered with a contained joy behind the crystal lens of his glasses. Science was that man's life. He was a brilliant person with a brilliant mind, and he had been waiting for an opportunity like this. _One day I'll get you into science, Sans._ he remembered Gaster promising time and time again. If Sans just bounced home, if he just teleported away, what would his father think? _He'd be so upset. It would be your fault, you know. Because you're a coward._

"Well, not much we can do to help that," Gaster went on. Sans wanted to sink into the ground, but he was only being pushed further towards the lab. "Hey, how about this? Let's make a deal: you spend today at the lab with me and if you don't like then I won't make you come back tomorrow. You can stay home." Sans nodded again. _That's fair._ He was shaking and he felt weak, but surely he could last one day. _One day in the lab._ Another shudder wracked his body. _But the offer still isn't enough_ _._

 _Because you're a cowardly little boy._

"So, is that a deal?"

"Yeah. It is. Thanks, Dad," Sans agreed quickly, hushing that voice in his head again. He didn't need his own imagination nagging him to know how much he would regret backing out now. _Don't disappoint Dad._

The conveyor ride was coming to its end. Gaster took Sans' hand in his own and led him onto the still, dusty ground in front of the lab. It was even bigger up close; if Gaster was a speck against it, Sans was as good as invisible.

Strangely, the lab didn't have a panel on its door like the elevator and CORE did. The door was just two slabs of smooth white metal that slid apart when the two skeletons approached. Sans knew that it was rigged with motion sensors, but he couldn't shake the feeling that the lab somehow knew that he was approaching, that he was entering a place he shouldn't be in…

 _Oh God, here I go._

The walls were pale and stretched far, far up before giving way to a high ceiling panelled with polished stone slabs. Lights dangled from thick metal wires and swung freely, illuminating the room in a soft white. Sans noticed that the floor beneath his feet was tiled in pale blue, and was shiny, apart from where he had stepped; his walking shoes were coated in a layer of red dust from outside.

Sans almost leapt back in shock when he felt Gaster nudge his side. "Whoops – sorry, Sans," he said, "But hey, it's not that bad, is it? Does that look scary to you?" He pointed one long, twiggy finger at a machine that Sans hadn't seen before. It was a near-black cube about the size of the television set up in his living room. On its front was a single unlabelled button and a cylindrical nub with a pinhole in the centre of the circle. Upon closer inspection, a white light could be seen shining from the hole when looked at from certain angles.

"What is it?" Sans asked, the pinpricks of light in his eye sockets seeming to dilate as he leaned in to inspect it. It certainly didn't look like it did much.

"I'm… Well, I'm not sure yet." Gaster admitted, once again rubbing at the crack in his skull as he put on that ginger, toothless grin again. "It was originally supposed to be a device for calculating the hex code of whatever colour is in its line of sight, but then I remembered we could just use a camera for that. I'm thinking of using the white laser for something."

"...Cool." Sans squinted at the machine again. He had to admit, it looked less scary than pathetic. A tiny box with an inquisitive, beady eye that blinked happily at him when he stared. In a way, it reminded him of Gaster.

"What about this?" The skeleton was crouching beside Sans again with another contraption in his hand. Another box, this time smaller and with a screen on the front that read, in a rather plain and robotic-looking font, _'09:12 20SEP 94'._ "It's a clock that does the date, too. And it lights up green on a holiday! Oh, and I've got to show you that all-in-one cutlery utensil that Rythe helped me put together..."

Somehow, despite everything, Sans found himself smiling. Not with the same fake grin that was always on his face – a _real_ smile. One that went all the way to his eyes. He was deathly frightened of the place, yes, but these inventions, the _ideas!_ They were such small trinkets with equally small functions, but it made Gaster so happy to show them off. Excited as a puppy, he would wander off and then reappear with new gadgets that he would then spend several minutes explaining, dismantling, showing Sans the circuitry. One of Gaster's slippers fell off as he scrambled away to fetch a new machine, and he was so preoccupied that he didn't even bother to go and put it back on.

"And it can even knit something other than a rectangle if you install a–" Gaster's lecture was cut off as the gentle _whirr_ of the opening doors drifted through the air. Chemblin had apparently finished running his errand, because he had returned to the lab and slipped on a pair of white latex gloves.

"Hey Doc, you ain't downstairs yet?"

"Ah, Chemblin! No, I was just showing Sans my newest knitting machine. I don't think you've seen this model before yourself, actually."

"Eh, I probably haven't. 'Ey Sans, just wait 'til you get downstairs. That's where all the real experiments go on." It was difficult to tell because of the shape of his face, but Sans thought he saw a gleam of deviltry in the young snake-monster's single eye.

"Oh, downstairs! Chemblin, why don't you take him down with you?" Gaster agreed, setting his knitting machine and wool aside to stand back up and regard his son from above. _The 'real' experiments?_

Chemblin nodded and cocked his head to one side. He rubbed his gloved paws together. "Sure, Doc. Kiddo, you're gon' like it. Explosions, acids and stuff? All downstairs."

Sans caught a sidelong glance from his father, who was squinting mischieviously behind his glasses. "You could say," he started, "That you're going to have a _blast."_ Chemblin half-snorted, half-cackled and then proceeded to converse with his boss, using words and terms that Sans didn't understand.

 _Explosions, acids and stuff, he_ echoed in his mind. Suddenly he remembered where he was. A laboratory in the middle of Hotland. A laboratory filled with liquids that could kill a hundred men with one drop. A laboratory made to appease the king with inventions and gizmos that would improve the lives of those trapped in the Underground. _Trapped, trapped._ That's what they were. Everyone was trapped in the Underground, and Sans was trapped in the laboratory where he was the only one who didn't know what was safe to touch and what could kill him. His knees began to shake again.

"Is Smoy still working downstairs?" Gaster chirped, the conversation suddenly changing tone.

"Yeah, I think he went in the second prep room. I ain't know what he's doin' there, but I guess he prob'ly does."

"Oh, good. I thought he might have gone home early again. He's been doing that a lot recently, and I'm running out of assistants, what with Rythe off on maternity leave."

Smoy. Sans had heard that name before, but never paid much attention to it. Perhaps Gaster had mentioned it on one of the bad days when he had come home complaining about the factories' failure to deliver iron, or maybe when he was trying to enthuse Sans about the wonders of science in one of his long lectures. _Well, he can't be that important, or else I'd remember him._ Rythe, however, was a name that Sans knew well – she was the yellow-skinned lizard lady who often brought home-baked quiche to share with the two skeletons. She was a seasoned cook, but certainly not a confident socialite. Rythe always seemed to be jumpy and determined to avoid eye contact, even with Gaster. That was fine with Sans, though - he didn't much like locking eyes with people, either.

"Sans," Gaster chimed suddenly. _Huh?_ "Let's go downstairs, why not? I want to show you the blasters I was talking about before."

Sans wasn't really in a position to say 'no'. He was sandwiched between the tall, eager skeleton and the snake-man who stared placidly at the boy as if waiting for him to simply move on and agree. He stammered a quick 'okay' and then let his father usher him into another elevator further towards the other exit.

 _Downstairs,_ he thought again, making an effort to keep his breaths stable, _Where all the real experiments happen._


	5. Chapter Four

**Chapter Four**

It was hard to remember what Sans had really been expecting of the basement. Perhaps a treasure trove of strange inventions that _whirr_ ed, _tick_ ed or _buzz_ ed at him with their gears and fans that counted the seconds or knitted scarves from colourful strands of wool. Maybe he was expecting a big, long table with a ridiculous chemistry setup placed atop of it – one of those cartoonish ones with the spherical flasks, winding glass tubes and bubbling multi-coloured liquids that fizzed and popped as they flowed.

Whatever he thought he would find down there, it certainly wasn't this. As soon as Chemblin and Gaster had led him out of the elevator, the light seemed to shrink away from the tiles beneath their feet, as though it were afraid of the basement's touch. There were no _whirrs_ or _ticks_ or _buzzes_ that Sans could hear. But he withdrew his hands from his pockets and held them in front as he walked, just in case there was some sort of deadly contraption waiting for him to walk into. It wouldn't surprise him. _This place is creepy._

 _You have to be careful with machines, Sans,_ Gaster had told him one time, long ago. _If you don't watch what you're doing, they could hurt you._ Sans didn't remember anything of the conversation beyond that vague warning – he didn't know what sort of machines Gaster was talking about or even to what degree of 'hurt' he was speaking of. He didn't want to take any risks. He didn't want to get hurt. _You coward._

"Dad?" Sans called with the voice of a lost mouse. He'd lost sight of his father in the darkness, and he couldn't tell who the person shuffling along beside him was. _Please don't be Chemblin,_ he willed, squinting to try and pick out a silhouette.

From somewhere ahead, Gaster's voice called back. "I'm going to check something, Sans. Stay with Chemblin for a while, all right?" _What!? No! What happened to the blasters?_ Sans tried to draw in a deep, silent breath in attempt to stop his bones from rattling. Chemblin couldn't know how afraid he was.

"'Ey kid, wrong way. We're goin' in the analysis room." the snake-man said, flicking what Sans assumed was his tail at him. He didn't know how Chemblin could even see in here. Maybe he had just memorised the entire floor. Reluctantly, the boy turned to face the direction of Chemblin's touch and started waddling forwards again, his hands still feeling in front like a pair of clumsy, heavy antennae.

"Why is it so dark, Mister Chemblin?" Sans hiccupped quietly, feeling something cold and hard scrape against his knee. He swerved to the right to avoid whatever it might have been. _Something big with great mashing gears and naked wires, something that could burn you or saw you in half..._

"Power shortage, I'm thinkin'. Use up so much energy with our machines, ain't none left for lights." Chemblin replied, flicking Sans with his tail again to guide him further along. Chemblin had no feet to make a sound, but every step sent a too-loud echo ringing through the room. If anyone else was in there, they would know exactly where he was. _There's that shivering again,_ the voice in his head mocked, _You coward, you coward, you coward, you_ _ **coward**_. Sans muttered a quick 'shut up' under his breath, silencing the words once more. They seemed to come back to bite him every few minutes. It was beginning to unnerve him that he couldn't really control his own thoughts.

"I think ya dad's workin' to fix that, tho'. Been fiddlin' with the CORE for a while now." Sans nodded absently, too immersed in his thoughts to take note that Chemblin couldn't see him. Of course the CORE was still being built; the number of monsters trapped in the Underground was ever-increasing, and therefore so was the demand for power. If Gaster hadn't employed all the hundreds of monsters that he had to maintain and expand the CORE, half of the population would still be living in the flickering shadows of candlelight and crystal-glow. _What sort of place even_ was _the Underground before the CORE was made?_ It must have been so dark and dismal.

Sans shuddered; it made him feel peculiar to think about how almost everything he saw was his father's influence. Every farm, every factory, every home with power – all there because of his father's doing. _I see why the king chose him to be the Royal Scientist._

"Agh, shit," Chemblin hissed suddenly, causing Sans to start. Chemblin slammed something against a nearby wall "Wrong door again."

 _Wrong door?_ "What's wrong?" Sans squeaked.

"Ah – nothin', kid. I'm just takin' you to the wrong place. I'm still new here, 'ey? Just forgot what direction we've headed for."

Sans' brow furrowed in thought. Light. They needed light. _Light, light! Oh!_

"C-can I try something, Mister Chemblin?"

"Try… somethin'? What sorta thing?"

"It's, um, a magic spell I learned at s-school. To make light."

"I guess. Knock yo'self out, just don't blow nothin' up."

Sans rolled up his left sleeve, then his right, trying to wipe the sweat from his hands as he did so. He didn't really expect the lab assistant to just allow him to perform a 'magic spell' without any questions; it was a rather ambiguous request. _But I don't want to walk around in the dark forever._

 _Please work. Please don't fail again._ He clapped his hands together, and a strange sort of energy buzzed all the way from his fingertips down to his toes. The pinpricks of light in Sans' eyes had flashed a luminous blue-yellow mixture, and when he pulled his hands apart, a globe of white light floated above each palm. The shadows shied away as the light spilled through the room.

Sans blinked, a little shocked. He'd only ever managed to do that trick correctly once before. The balls of light were already fading back into nothingness, but nevertheless, it was an impressive feat. And he had managed to catch a glimpse of the room's layout. It was nearly square-shaped, with just a couple of rusted inventions lying in a heap in the corner and several doors built into the walls around. The floor tiles were a darker shade of green, but other than that it looked about the same as upstairs.

In the brief moment when light illuminated his the area, Sans caught Chemblin mouthing something along the lines of 'what the fuck' – some sort of crude exclamation of awe, at least. The skeleton boy didn't know whether to feel smug or nervous.

"Where the hell'd ya learn that? God on a bike, kid."

"School," Sans answered, shrinking back again. He decided to feel nervous. Chemblin's language didn't sound as friendly as it had before.

"No flamin' way, jeez. I wish they'd gone an' taught me that. Can ya do it again? I might'a missed the door when I was lookin'."


	6. Chapter Five

**Chapter Five**

Sans held out his hands and cast the spell again. Once more the room was bathed in light, then plunged into darkness. He did it again. Light, dark. Again, again. Light, dark, light, dark. His eyes were strobing blue and white, and his breaths were coming heavy. The excessive use of magic was making him feel weak. It was straining him to keep going. Light, dark, light, dark.

He could barely follow Chemblin as the snake-man led him through the room towards another door on the far side of the adjacent wall, but eventually the lab assistant gave Sans the signal to stop. The skeleton dropped his arms to his sides and panted hard as the room was plunged into an inky blackness again.

"Cheers, Sans," Chemblin said, stopping abruptly and causing Sans to walk into him. "That was pretty impressin'. Anyhows, this is the place."

"The – the analysis room, right?"

"Yeah. That's the ticket." Sans started to ask a question – something along the lines of 'what's in there?' – but he had no time to wonder, for Chemblin had turned the door handle and opened a path to the room ahead.

The lights in this room were out of use, too, but Sans could still see inside by the light of various screens bolted to the wall. The screens all displayed long strings of number sequences and strange words made up of strange characters. Beneath the screens was a long desk, also attached to the wall, that stretched all the way to the end of the room. Atop the desk sat several smaller devices that Sans recognised to be microscopes. Other tables in the room were home to yet more microscopes and a range of equipment that looked like an array of objects from a sci-fi film.

 _Microscope, screen, microscope, power pack. Slides, dye, thermometers, power pack._ As he was led through the room, he made a point of trying to name everything that he saw. _Microscope, slides, screens, needles._

"Chemblin." Someone spoke up ahead. The voice was monotone and shallow, yet low. It reminded Sans of the droning hum of electricity.

Sans strained his eyes, trying to see what the voice's owner looked like. He made out the faint outlines of a short man with short arms and eyes that bulged from the top of his head sitting at a stool. _A lab assistant,_ Sans thought, _but one I haven't met._

"Who's he?" the stranger asked, gesturing forwards with one arm. Sans whipped around to check behind him. There was nobody else there but him and Chemblin. _He's talking about me?_

"Gaster's boy," Chemblin called back. The stranger's forehead puckered in a frown, but he held his tongue and allowed Chemblin to continue. "Doc asked me to look after 'um, but I ain't sure where he was wantin' me to take him."

Slowly, the stranger reached out and beckoned Sans forwards with a finger. When Sans froze, the man called out. "Come here, child." The boy drifted forwards and felt the stranger's thick, stubby fingers curl around his shoulder. The two locked eyes for a moment, but then the man allowed a sigh to pass his lips and moved away. He started to prepare a microscope slide, seemingly forgetting about Sans' presence.

"I'll take him off your hands," the man said again after a while. His eyes were still trained on the slide, which he was now attempting to set above the microscope's light. "After all, Chemblin, you have work to do."

Sans tensed. The man wasn't looking at him, and yet he suddenly felt naked in front of this stranger, and gripped at his shirt to cover the flat bone between his ribs. It seemed as though he were being searched. _Don't be stupid. He's more interested in the microscope._

"What sorta work you got in mind?" Chemblin chimed, shoving his paws into the pockets of his lab coat. "Cleanin' again?"

"The bio lab needs sterilising. I'm planning to perform an incubation later."

"That's tha' far door, right?"

"The one opposite the elevator."

"Got'cha. 'Kay, I'll be back in a couple hours, Sans." Sans ducked his chin and waited for Chemblin's exit. The snake-man slammed the door closed behind him, trapping Sans in the room with the stranger.

He suddenly felt very out of place. The screens blinked and flashed pictures of some strange sort of material, and the stranger was engrossed in his work with one eye placed over the microscope lens. Everything was working in its place but for Sans, who might as well have been invisible for all the attention that the frog-eyed scientist was paying him.

Just as he was about to speak, Sans was interrupted by the man's flat, droning voice again. "Do you like science, child?" The boy looked away but gave two quick nods. He found himself wringing his hands again, and made a point of pulling them apart to allow them to dangle loosely at his sides.

"M-my dad teaches me a lot. At home. Especially about things like human biology, and –"

"Yes. I know." The man allowed several minutes of unnerving silence to creep by before he spoke again. "It's nice to meet you, Sans. I've been wanting to see you in person for a while."

"Thanks, uh, I.."

"My name's Smoy." _My name's Smoy. Smoy, Smoy…_ That was the name that Sans had heard so many times in the past, but never paid attention to. A lab assistant who had worked with his father for a long time, but not someone like Rythe, who often came to visit outside of working hours.

"Are you friends?" Sans coughed, trying to look everywhere but at Smoy. _He still won't look at me. He doesn't want to talk. I'm not supposed to be here._ "Like, um, he talks about you sometimes. M-my dad, I mean…"

"Sometimes." Sans blinked owlishly and furrowed his brow in thought.

"So you a-argue a lot, then..." the boy thought out loud. Gaster was the least argumentative person he knew. Maybe he just acted differently around Sans. _For my sake._

"Not really," Smoy sighed, finally tearing his eyes away from his work. They were bloodshot, puffy at the edges. They were probably red, too, but Sans couldn't tell with the dimness of the lighting. "I'm just friends with another Dings."

"I thought there was only one person called Dings."

"There is. Hmph, look – I don't want to confuse you. Just look after your father for me. He's a nice person."

"O-okay."

Smoy returned to his work. He set up a new slide at another microscope and then examined the strange clusters of cells that flickered on the screens ahead. Sans began to wonder if Smoy had forgotten that he was standing there.

"Have you ever used a microscope, Sans?" Smoy chirped suddenly.

"We have microscopes at school." said Sans.

"Ah. Why don't you have a look in this one? I think you'll like what you see."

Sans leaned towards the microscope as Smoy backed away. When the man stood up, he was almost as short as Sans was. Smoy could probably even class as a child if he didn't have dark shadows under his eyes that told stories of anxiety and insomnia and perpetual fatigue…

One eye stretched open and the other socket squeezed shut, Sans peered into the lens. It was another cluster of cells. But this one looked _different._

"What type of animal is this from, Mister Smoy?" he asked, his hands finding the knobs towards the back. He began to fiddle with the focus.

"That tissue? We took it from a human."

 _What!?_

"A h-human?" The words came spilling out from between Sans' clenched teeth. He couldn't stop himself from echoing those words as had just been said. "A human? A real one?"

Smoy's eyes narrowed and he gazed placidly at the screen ahead, but the edges of his mouth were tight and slightly raised. "Yes. But it's with the king at the moment."

"Oh, okay… Whoa…"

"They look different, don't they? It's because there's no magic inside them. They need all sorts of little machines to do all sorts of jobs."

Sans nodded, his eyes glazed and deep with thought. _So humans_ do _fall down here. But it's with the king. With the king…_

"Smoy?"

"Yes?"

"You said it's with the king."

That same narrow-eyed, tight-lipped expression found its way back to Smoy's tired face. "Don't worry, Sans. Asgore will kill it when we're done with our research."


End file.
